Bug 995374 - Update virtualenv to 1.11.4; r=mshal

We're trying to stay up to date on virtualenv releases so we don't fall
too far behind and so we can leverage new features, such as wheels.

This virtualenv release features upgrades to pip (1.4.1 to 1.5.4) and
setuptools (0.9.8 to 2.2). These may fix bugs people are encountering
in the wild.

Tarball obtained from
https://pypi.python.org/packages/source/v/virtualenv/virtualenv-1.11.4.tar.gz#md5=9accc2d3f0ec1da479ce2c3d1fdff06e.
the egg-info directory was removed (consistent with previous virtualenv
upgrades).

--HG--
extra : rebase_source : 0cef066c747d51b8f47e4218353dd47f391ff831
extra : amend_source : 08a255f64093e9280da04a4bead2db3e6f9abe42